This invention relates to an insert pin used in an insert molding apparatus which holds a terminal inserted in a mold when forming an insert molded product.
As shown in FIGS. 1 to 3, for forming an insert molded product 30, having terminals 18 therein, by a conventional method, the terminals 18 are placed within a mold 20, and insert pins 31 are inserted respectively through pin holes 21 in the mold 20, and each terminal 18 is pressed by one end of the insert pin 31. Therefore, the insert pins 31 hold the terminals 18 against the flow of a resin material 19, poured through a gate 22 in the mold 20, so that the terminals 18 will not be moved. Then, the resin material, poured into the mold 20, is cooled and cured in the sequence from the downstream-side resin material 19' kept in a stationary condition.
However, the resin material 19 has a high viscosity, and the insert pin 31 is formed into a circular cross-section, and therefore the resistance, applied from the flow of the resin material 19, is large at the downstream side 32 of the insert pin 31. As a result, a weld line (that is, a stripe extending in the direction of the flow) 33 is formed in the direction P of the flow during the molding of the insert molded product 30, and therefore there has been a possibility that a crack or the like develops in the weld line 33 during an endurance test (e.g. thermal shock test).